In some wireless communication systems, when data that is transmitted by a transmitting entity to a receiving entity is not received by the receiving entity, or is received by the receiving entity with one or more errors, the data may be re-transmitted. The re-transmission of data could occur either automatically or in response to feedback from the receiving entity. For example, a Hybrid Automatic Repeat Request (HARQ) procedure could be used. In the HARQ approach, after a transmitting entity has transmitted a block of data, the transmitting entity waits to receive a HARQ response from the receiving entity. If the transmitting entity receives a positive acknowledgement (ACK) as the HARQ response, then no re-transmission is needed and the transmitting entity can transmit additional data. If the transmitting entity receives a negative acknowledgement (NACK) as the HARQ response, then the transmitting entity re-transmits the data. The transmitting entity may also re-transmit the data if the transmitting entity does not receive any HARQ response within a certain period of time.
This re-transmission approach can allow data to be successfully transmitted from a transmitting entity to a receiving entity even when there is a substantial probability that the transmitted data will be received with one or more errors, for example, because of poor radio frequency (RF) conditions. Specifically, the data can be re-transmitted multiple times until the data is received without errors. Further, in some implementations, the transmitting entity could include forward-error-correction (FEC) bits with each transmission attempt, and the receiving entity could combine multiple such transmissions together to help successfully recover the intended transmission.
In a representative implementation of this process, the receiving entity may be configured to transmit a HARQ response to the transmitting entity at a defined time following the transmitting entity's transmission of the data. This time may be set so as to allow sufficient time for the receiving entity to process a received data transmission so as to determine whether the transmission is error free or whether re-transmission is necessary, and for transmission of a HARQ response to the transmitting entity. Further, by having the receiving entity transmit the HARQ response at the defined time following the data transmission, the transmitting entity could understand that a HARQ response received from the receiving entity at that defined time corresponds with the transmission at issue, so that the transmitting entity can then proceed as necessary.
In addition, the transmitting entity may be configured to engage in re-transmission or a next data transmission at a defined time following the receiving entity's transmission of a HARQ response. This time may be set to allow sufficient time for the transmitting entity to process the received HARQ response (or detect absence of such a response) and to prepare for re-transmission or a next data transmission.
Further, in a representative implementation, the transmitting and receiving entities may be configured to allow up to a maximum number of HARQ re-transmissions for a given data transmission. For instance, the maximum number might be set in a range of zero (meaning that no HARQ re-transmission is allowed) to eight (meaning that eight re-transmissions could occur).